Saudi Arabia is preparing to acknowledge the death of Saudi journalist Jamal Khashoggi happened as the result of a botched interrogation, according to CNN and The New York Times, after US President Donald Trump speculated "rogue killers" may be responsible.

Key points:

Mr Trump says Mr Pompeo may also visit Turkey during the trip

He says it sounded like "rogue killers" were involved in Khashoggi's disappearance

The US President says Saudi monarch King Salman has "denied any knowledge"

Khashoggi, a US resident, Washington Post columnist and leading critic of the powerful Saudi crown prince, Mohammed bin Salman, vanished after entering the Saudi consulate in Istanbul two weeks ago to get marriage documents.

Members of Khashoggi's family called for an investigation in a statement released on Monday.

"We are sadly and anxiously following the conflicting news regarding the fate of our father after losing contact with him two weeks ago," they said.

"The strong moral and legal responsibility which our father instilled in us obliges us to call for the establishment of an independent and impartial international commission to inquire into the circumstances of his death."

Citing two unidentified sources, CNN reported that Saudi Arabia was preparing a report that would acknowledge Khashoggi was killed as the result of an interrogation that went wrong.

The Saudi Government could not be reached immediately for comment on the CNN report, but Mr Trump said he was unsure whether it was official.

"I heard that report, but nobody knows if it's an official report," Mr Trump said, without elaborating, while visiting Florida to inspect the damage from Hurricane Michael.

The New York Times, citing a person familiar with the Saudi plans, reported the crown prince had approved an interrogation or rendition of Khashoggi back to Saudi Arabia.

The Saudi Government, it said, would shield the prince by blaming an intelligence official for the bungled operation.

Turkish authorities have an audio recording indicating that Khashoggi was killed in the consulate, a Turkish official and a security source said, and have shared evidence with countries including Saudi Arabia and the United States. They provided no further details.